The drug, crizotinib, targets a protein found in around five in 100 patients with the most common type of lung cancer.

Typically, these patients are much younger than average and do not appear to have a disease closely linked to smoking.

Marketed as Xalkori, the treatment was given an early licence by regulators after promising trial findings.

A Phase III study of 347 patients found that the drug more than doubled the time taken for treated tumours to start growing again or stop shrinking.

So-called “progression free survival” was increased from a mid-point of three months for patients on chemotherapy to 7.7 months.

Although survival time was not studied, researchers believe the drug has the potential to extend lives.

Crizotinib is the latest in a new generation of cancer drugs tailored to individuals with specific genetic make-ups.

It acts on a protein called ALK which blocks anti-cancer signalling pathways.

Patients who can benefit from crizotinib are identified by analysing biopsy tissue samples. They form a distinct subgroup among patients with non-small cell lung cancer, which accounts for 80-85% of lung cancer cases.